1. Field of the Invention
This invention relates in general to air bearing sliders for use with recording media and more particularly, to a slider having air bearing surface features which minimize the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
2. Description of Related Art
Conventional magnetic disk drives are information storage devices which utilize at least one rotatable magnetic media disk with concentric data tracks, a read/write transducer for reading and writing data on the various tracks, an air bearing slider for holding the transducer adjacent to the track generally in a flying mode above the media, a suspension for resiliently holding the air bearing slider and the transducer over the data tracks, and a positioning actuator connected to the suspension for moving the transducer across the media to the desired data track and maintaining the transducer over the data track during a read or a write operation.
In magnetic recording technology, it is continually desired to improve the areal density at which information can be recorded and reliably read. Because the recording density of a magnetic disk drive is limited by the distance between the transducer and the magnetic media, a goal of air bearing slider design is to xe2x80x9cflyxe2x80x9d an air bearing slider as closely as possible to a magnetic medium while avoiding physical impact with the medium. Smaller spacings, or xe2x80x9cfly heightsxe2x80x9d, are desired so that the transducer can distinguish between the magnetic fields emanating from closely spaced regions on the disk.
Zone bit recording can provide significant performance and capacity improvements in magnetic disk storage files. In order to facilitate this technology, it is desirable to maintain a constant spacing between the read/write head and the disk across all the zones, from the inner-diameter (ID) to the outer-diameter (OD) of the disk. It is also desirable to fly as low as possible across the data zones to increase amplitude and resolution and further increase areal density and file capacity. However, low fly height causes concerns over mechanical reliability in the file, for both start/stop life and long term flyability.
Constant flying heights across the data zones presents a substantial challenge to slider design because the air velocity created by the rotating disk varies in both magnitude and direction relative to the air bearing slider at all radii in rotary actuator files.
An air-bearing slider also experiences fly height variations due to roll. For an air bearing slider with zero skew relative to disk rotation, roll is a measure of the angle of rotation about the longitudinal axis of the air bearing slider. Variations in roll occur when a resiliently mounted slider experiences a skewed air flow or the actuator experiences an impact with the disk. Insensitivity to roll variations is a crucial requirement of air bearing sliders.
Finally, an air bearing slider experiences varying conditions during the high speed radial movement of the actuator as it accesses data on various portions of the disk. High speed movement across the disk can lead to large values of slider roll, pitch and skew and a resultant variation in fly height. This is yet another reason that an air bearing slider must be insensitive to changes in roll, pitch and skew.
Typical taper-flat type sliders cannot satisfy the constant spacing requirements for zone-bit recording. For most rotary actuator configurations, the taper-flat slider flying height increases rapidly as the head is moved out from the ID. As it approaches the middle of the data band, it reaches a maximum spacing, which may be up to twice as large as the initial ID flying height. From there, the clearance drops as the air bearing slider moves toward the outer rim of the disk.
When any of the above described variations in fly height occur, they may result in contact between the air bearing slider and the rapidly rotating recording medium. Any such contact leads to wear of the air bearing slider and the recording surface and is potentially catastrophic.
Prior art slider designs have attempted to avoid this problem by addressing one or more of above described sensitivities, so as to produce an air bearing slider with uniform flying height under the varying conditions that may be experienced by the air bearing slider. Alternative designs for the air bearing surfaces have been developed to provide the required aerodynamic performance. Further, these designs frequently utilize trade-offs between the slider""s pitch and roll to achieve the flat head/disk spacing desired. However, the rail width which provides the air bearing surface must also be capable of accommodating the read/write transducer. Consequently, variations in the slider""s flying attitude can result in a much lower mechanical slider/disk spacing with a corresponding increase to the magnetic head/disk spacing.
For example, FIG. 1a illustrates a prior art slider 10 having a leading edge 12, a trailing edge 14 and two side edges 16, 18. As the disk begins to rotate, the slider pitches such that the leading edge 12 is raised with respect to the trailing edge 14 as shown in FIG. 1a. The slider illustrated in FIG. 1a includes two side rails 20, 22 and a center rail 24 for a given performance standard. The two side rails 20, 22 and the center rail 24 are disposed on a support structure 26. A transducer 28 is disposed on the center rail 24 at the trailing edge 14 for performing read/write operations on the disk. FIG. 1b illustrates a close-up view of the center rail 24 at the trailing edge 14 of the slider 10. The head gap 32 of the transducer 28 is also shown. Under the above described conditions, the slider may experience roll, indicated by longitudinal displacement angle 34, which may cause the slider to contact the rotating disk due to the much lower mechanical slider/disk spacing. FIG. 2 illustrates how a nominal roll angle 34 causes the mechanical spacing of the center rail edge 42 to be substantially lower than the magnetic gap flying height.
FIG. 2. illustrates a rear view of the prior art slider 10 along lines Axe2x80x94A of FIG. 1a. The view in FIG. 2 is exaggerated for clarity. In FIG. 2, the center rail 24 is shown disposed on the support structure 26. As the slider 10 experiences a nominal roll angle 34, the mechanical spacing 40 between the edge 42 of the center rail 24 and the disk 44 decreases while the magnetic spacing 46 between the head gap 48 and the disk 44 decreases to a lesser degree, remains the same or becomes greater depending upon whether the axis of the roll is displaced from the slider""s central longitudinal axis. FIG. 2 illustrates the situation where the magnetic spacing 46 between the head gap 48 and the disk 44 becomes greater. The magnitude of the difference between the mechanical spacing 40 and the magnetic gap flying height 48 can be substantial. For example, a slider with a 400 xcexcm trailing edge rail width and a nominal 50 xcexcrad flying roll attitude will have a minimum mechanical spacing 40 that is ten nanometers (nm) lower than the desired magnetic spacing 46 fly height causing the slider to be raised for increased wear resistance, i.e., increased life-time.
It can be seen then that there is a need for a slider that has air bearing surface features which minimize the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
It can also be seen that there is a need for a slider having shallow etch features that allow optimization of transducer spacing.
It can also be seen that there is a need for a disk drive having a slider which exhibits a narrow trailing edge rail while still providing adequate area for the read/write transducer thereby minimizing the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a shallow etch at the trailing edge rail that allows the slider to fly closer to the recording medium.
A system in accordance with the principles of the present invention comprises a support structure having side edges, a leading and a trailing edge relative to the motion of the recording medium and at least one rail having side edges and an air bearing surface raised above the support structure, wherein at least one of the rails comprises a magnetic element, and wherein the edges of the rail adjacent to the magnetic element are etched to minimize the fly height of the magnetic element over the disk while preventing collision of the rail with the disk during roll conditions. The etched features of the rail create relieved trailing edge portions where the edges of the rail adjacent to the magnetic element may be lower than other air bearing surfaces but are higher than the support structure.
One aspect of the present invention is that the slider has air bearing features which minimize the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
Another aspect of the present invention is that the slider has shallow etch features that allow optimization of transducer spacing.
Another aspect of the present invention is that a disk drive may include a slider which exhibits a rail with a narrow trailing edge while still providing adequate area for the read/write transducer thereby minimizing the difference between the minimum mechanical slider/disk spacing and the magnetic head/disk spacing.
In an alternative embodiment the edges of the air bearing surface adjacent the magnetic element are shortened by etching or ion milling, i.e., they do not completely extend to the trailing edge.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.